Tapering an optical waveguide (also known in many instances as an optical fiber) below its transmission cutoff diameter causes the propagating light to form an evanescent field at the waveguide tip. If nothing couples to this evanescent field, the propagating light undergoes total internal reflection (TIR) and returns to the light source. If any evanescent field coupling occurs the amount of reflected light is proportionally reduced. Near-field scanning optical microscopy (NSOM) uses this phenomenon to achieve spatial resolution performance beyond the classical diffraction limit by employing a sub-wavelength light source or detector positioned in close proximity to a specimen.
Individual optical waveguides have been drawn down to approximately 100 nm and addressed optically as microscopy or sensor probes. In certain applications, it is desirable to scan a large area. In other applications it is desirable to probe many regions over an area simultaneously. Unfortunately, scanning a large area using a single probe is time consuming because of the small size of the probes. In addition, individual probes cannot simultaneously probe many regions over a given area. What is needed is a microscope or sensor probe design which provides a large number of sharp tips oriented in parallel that is operable for scanning a large area quickly, permitting simultaneous probing of many regions over a given area.